When personal computers became sufficiently small to allow user portability, it became necessary to provide connections between a portable computer and a computer network system. Traditionally, the portable computer uses a Personal Computer Memory Card International Association (PCMCIA) card for either an Ethernet or Token Ring network hard wire connection.
Recently, both portable computers and computer networks include infrared transceivers that allow wireless communication between the portable computer and the computer network for increased mobility. The computer network includes a protocol conversion bridge that converts communicated data between an infrared protocol and a protocol of the computer network. The protocol conversion bridge is coupled to a connector typically near the user's work station. The connector is then coupled to a network hub that is centrally located. A dedicated electrical power supply located near the bridge and the infrared transceiver provides electrical power to the protocol conversion bridge. The dedicated electrical power supply increases the system cost and requires an AC electrical power outlet.
Several systems provide both electrical power and signals over a common wire. For example, conventional telephone systems that use 48V on a telephone wire transmit both electrical power and communication signals over a single pair of lines. U.S. Pat. No. 5,444,184 describes a system that transmits both electrical power and low baud rate signals over the same twisted-pair wires. An attachment unit interface (AUI) in LAN applications uses dedicated wires in a cable to provide electrical power from a data terminal equipment (DTE) to an external medium attachment unit (MAU) which could be 50 meters away from the DTE. All of these systems simply provide electrical power over the wires. None of these systems checks or confirms the type of system connected thereto before supplying the electrical power.
Standard network protocols may be described in an Open System Interconnection (OSI) interface standard. One standard network protocol is the Ethernet which is described in IEEE standard 802.3 CSMA/CD, the subject matter of which is incorporated by reference in its entirety. Another standard network protocol is the Token Ring protocol which is described in ANSI/IEEE standard 802.5, the subject matter of which is incorporated by reference in its entirety. Both of these IEEE standards describe the media access control (MAC) layer and the physical layer of the OSI interface.
FIG. 1 is a pictorial view of the interface layers of the OSI standard. For simplicity, layer 3 through layer 7 of the OSI are combined as higher layers 139. Layer 2 of the OSI interface comprises the data link control (DLC) which includes a logical link control (LLC) layer 138 and a media access control (MAC) layer 134. Physical layer 1 of the OSI interface comprises several sublayers including an attachment unit interface (AUI). The AUI is specified for a 10 Mb/s Ethernet but not for a 100 Mb/s Ethernet. A media attachment unit (MAU) 142 includes all of the physical sublayers other than signaling and coding sublayer. In a twisted-pair cable, the medium dependent interface MDI 144 is an RJ45 connector.
Many conventional network systems detect either layer 1 or 2 that the data terminal equipment 130 supports. This detection allows the network systems to share circuitry, connectors, and the medium so that the network systems may handle multiple protocols. By sharing, the cost of the DTE is reduced and the inconvenience or damage is minimized when misconnection is made to the wrong connector. However, all of these conventional systems presume that the DTE conforms to the IEEE Standards. Accordingly, these detection systems test only systems that comply with the IEEE Standards. Depending on the range of the layers that these systems want to detect, the systems require a different degree of involvement and resources includes central processing units, software codes and flow, system bus, memory, protocol handler, and transceivers. The system also is protocol dependent and the DTE must run only the protocols that the system can understand. The systems are not intended, nor do they function to detect an electronic system which is not in conformance with IEEE Standards.
U.S. Pat. No. 5,497,460 discloses a detection mechanism that allows two different media access control layer protocols (Ethernet and Token Ring) to share the same connector and medium in the OSI model of FIG. 1. The detection scheme requires a sophisticated processing unit that issues a protocol dependent MAC frame and physical signals and compares a predefined status in memory to determine which one of the two presumed protocols runs on the twisted-pair cable. The detection scheme cannot communicate with any device which does not conform with Ethernet or Token Ring.
Under the same Ethernet MAC protocol, U.S. Pat. No. 5,410,535 describes a device that differentiates between mediums that the device is connected to so that the connected devices may share the same connector. The medium in this case could be a twisted-pair cable or AUI for other medium types. The control flow and logic manufactured in silicon are Ethernet physical layer dependent. U.S. Pat. No. 5,541,957 includes a separate physical layer logic to allow two Ethernet connections operating at different transfer rates to share the same connector.
U.S. Pat. No. 5,121,482 describes a device that detects the connected device independent of networking protocol. But its detection mechanism relies on the impedance of the data signal lines, its detection circuitry is also coupled directly to the data signal line, which may lead to interference or even corruption on the communication link when running the detection procedure.
It is desired to have a network system that recognizes remote devices connected to a connector of the network system in real time without intruding on the normal operation, provides appropriate electrical power as required without damaging the connected remote device, and automatically connects the device to a network hub running an appropriate protocol.